1. Field of Invention
The subject invention concerns a high speed air pump for supplying combustion air to an internal combustion engine. More particularly, it relates to a frictional drive mechanism for the air pump for generating a high step-up speed ratio so that the pump is rotated at many times the input speed.
2. Description of the Related Art
In the internal combustion engine art, accessory components are typically driven by the crankshaft of the engine through belts which pass about pulleys on the crankshaft and on a shaft of an accessory. With such a belt drive it is relatively easy to step-up the rotation speed of the accessory shaft using differential sized pulleys. Typically, this is sufficient to step-up rotational speeds by fairly low ratios, such as 2:1 for example. however, when higher step-up ratios are desired, it is not considered possible using differential sized pulleys alone.
The subject engine air pump is a high speed, turbine type pump which can require a rotational speed about 16 times the engine crankshaft speed to be effective. With such a ratio, an engine idle speed of 750 RPM would produce a pump speed of 12,000 RPM. At an engine speed of 5600 RPM, the pump would rotate at 90,000 RPM. Even if a belt/pulley combination alone could produce this high 16:1 ratio, resultant forces on the belt would prevent using such an arrangement.
A desirable solution to the above identified pump drive problem is to provide a frictional drive mechanism. Of course, there are many examples of various frictional drives known in the prior art. For example, applicant is aware of the following prior U.S. Patents which use a friction drive: U.S. Pat. No. 2,490,667 to Boyd; U.S. Pat. No. 2,732,724 to Tateishi; U.S. Pat. No. 2,781,667 to Giskes; U.S. Pat. No. 3,267,757 to Hammerrand; U.S. Pat. No. 3,289,487 to Weedfall; and U.S. Pat. No. 3,971,262 to Altrogge. These patents relate to relatively low speed, low torque applications of a friction drive and do not teach the arrangement of components to successfully achieve the results necessary in the engine pump drive which is the subject of this application as will be made clearer hereinafter.